After answering a question in the comment section of the Hafler DH-110 Preamplifier Refresh. I decided to design a board to hold surface mount film capacitors for capacitors C19 and C119.
Hafler DH-110 Pre-amp Filter Boards
Transistor matching test fixture
I had the need to match a batch of transistor pairs for a project, so I designed a circuit board based on a circuit by Ian Fritz.
Nakamichi 420 Amplifier Salvage
I have had my Nakamichi 420 audio amplifier since the late 70’s, and have used it with no issues since it’s purchase. Recently I was listening to an album, when it quit producing any sound, and shortly after produced that burnt electronics smell we know so well.
Power Designs D‑series display board update
After the acquisition of my Power Designs 5015D power supply, I really wanted to upgrade the display module so that I had an extra digit of resolution. I already had a few ADC/LED meter boards left over from previous projects, but needed a display board to pair with it.
Fixing Up a Hewlett Packard 1662C Logic Analyzer
Cleanup and mechanical repairs on a 1996 vintage HP 1662C Logic Analyzer to add to my test equipment collection.
Hewlett Packard 34721B BCD Module
Adding a new HP 34700 series module to the collection. This time it is the 34721B BCD interface plug-between module, which converts character serial data from the 34740A or 34750A Display Module to parallel character information for output to a printer.
Davis VantagePro2 Weather Station Repair
Repairing some Davis Vantage Pro2 ISS transmitter boards that have stopped transmitting at night.
Hewlett Packard 3551A Transmission Test Set
Checking out a HP 3551A sold as “For parts or not working, will not power on”, that I actually purchased for parts.
My original intent on purchasing this unit was to salvage the knobs and connectors for repairing some of my other HP gear. I did manage to swap out four of the knobs before my curiosity got the better of me.
Hewlett Packard 8012B Pulse Generator
Cleanup and repair of a Hewlett Packard (HP) 8012B pulse generator purchased on Ebay as “Untested does not power on, sold as is”.
The 8012B was originally produced by the HP Gmbh Boeblingen Divison, Germany, but this later model was made in USA. It provides variable transition times down to 5 ns and the repetition rate can be adjusted from 1 Hz to 50 MHz.
Hewlett Packard 10548A Diagnostic Service Kit
After spending many hours working on my Hewlett Packard 5300 series measuring systems, I decided to remake my own version of the HP 10548A diagnostic service kit.
HP 5300B Counter Plug-On modules
Cleaning up and looking at a bunch of plug-on modules for my Hewlett Packard 5300B mainframe modules, after purchasing a new unit. It seems that I am starting to collect quite the range of modules for my HP 5300 systems since my original 5300B Measuring System back in 2017.
Isolated TTL Serial to USB 2.0 Converter
After using my last commercially made isolated TTL serial to USB converter for my last project, with no hopes of it being re-stocked in the near future. I decided to try building my own version of the device.
Updating the Programmable Voltage Reference Project
After five years and a few prototype revisions of the Version 2.12 Programmable Voltage reference, I decided it was time to update the project based on many requests and lessons learned from prototypes over the years.
Updated PIC32 based VT100 ASCII Video Terminal
After building the ASCII Video Terminal Kit, I decided to create an updated circuit board based on the original Geoff Graham ASCII Video Terminal project, which was then later updated by Peter Hizalev and sold on Tindie.
Remake of the Hewlett Packard 11456A Read Out Test Card
The HP 11456A Read Out Test Card is a nifty little test board that plugs into the HP 3470 series display modules. I really wish that I had had one of these, before I started working on my faulty HP 34740A display module.
HP 34740A display and 34702A Multimeter Modules
As mentioned in a previous post on the Hewlett Packard 34702A Multimeter module, I have been looking for a 34740A display module to pair with it. I was lucky to find a module that was in a good cosmetic condition and untested for a reasonable price.
